The chemical synthesis of 2'(3')-O-aminoacyloligoribonucleotides and 2'(3')-O-(N-acylaminoacyl)oligoribonucleotides with nucleotide sequences identical to or resembling those of the 3' terminus of AA-tRNA will be carried out. These compounds will be used as models of the 3' terminus of AA-tRNA or peptidyl-tRNA in order to study their involvement in the various steps of protein biosynthesis on ribosomes and their interactions with elongation factors (EF-Tu, P and G). Modified tRNA containing "fraudulent" nucleoside units on the 3' terminus will be synthesized by combination of chemical and enzymatic methods. These modified tRNAs will be used for study of various subreactions of protein biosynthesis.